Final Quiz
The total diameter of our galactic disk is about
100,000 light years
How far is it across the Milky Way Galaxy?
100,000 light years across
When was the Nuclear Test Ban Treaty signed, forbidding nuclear weapons in space?
1963
When did the Dutch-Italian satellite BeppoSAX first resolve the origin of a GRB?
1997
How long is the cylindrical bar of red stars at the center of our galaxy?
20,000 light years long.
How long does our Sun take to orbit the galaxy?
250 million years
We still classify galaxies according to Hubble's original system, based on
4 major types of galaxies.
Stars that could one day explode as gamma-ray bursts can only hurt us if they are
7000 light-years away.
How long did the gamma-ray bursts, detected by Vela, last?
A couple seconds.
What appears to be at the heart of every big galaxy we see?
A huge black hole.
What sits right at the center of many galaxy clusters?
A huge elliptical galaxy
The extremely high velocity orbits of stars at the center of our Galaxy are thought to be caused by what?
A supermassive black hole
Which of the following is not believed to be one of the components of our galaxy?
An active galactic nucleus (AGN)
What sort of geometry is believed to lead to Blazars, also known as BL Lacartae Objects?
An active galaxy where we happen to be right in line with one of the jets
What is the name of the other large galaxy in our galaxy group or cluster (not our galaxy)?
Andromeda
In the 1920's it was determined that the "Great Andromeda Nebula" was actually the
Andromeda Galaxy
Which of the following is a likely consequence of two galaxies colliding?
Both gas clouds collide and galaxies merge, but individual stars do not merge
Collisions between galaxies can
Cause bursts of star formation
Which distance method can be used to find the distance to nearby galaxies, such as Andromeda?
Cepheid variable stars
In the 1920's, what type of pulsating stars were observed in the spiral nebula M31?
Cepheid variables
What is believed to be the cause of the spiral structure in spiral and barred spiral galaxies
Density waves - the gravitational attraction of high density waves makes them self propagating
Which astronomers "unlocked the mystery" of spiral nebulae?
Edwin Hubble and Milton Humason.
Which shape are the largest galaxies in the Universe?
Elliptical
What type of galaxy is puffy, with no overall structure and populated with older stars?
Ellipticals
Which astronomer discovered that the Milky Way was actually made up of stars?
Galileo.
1. What "balls of stars" helped determine that the Sun wasn't at the center of the galaxy?
Globular clusters
Where are we, Earthlings, located in the Milky Way Galaxy?
Halfway out from the center in the suburbs
Which astronomer argued, in 1920, that "the Milky Way was all there is"?
Harlow Shapley
How many stars are in the Milky Way Galaxy?
Hundreds of billions of stars
What type of galaxy tends to be small and are truly shapeless?
Irregular galaxies
What image, taken in 1995, shows a small grain of the sky filled with thousands of galaxies?
It was a picture of the Hubble Deep Field.
The Vela satellites detected a mysterious flash of gamma rays on
July 2, 1967
Which of the following statements about the Milky Way's globular clusters is FALSE?
Like open clusters, Globular Clusters are found only in the Galaxy's disk
What name is given to the merger of the Milky Way and the Andromeda Galaxy?
Milkomeda.
What is the name of the galaxy we live in?
Milky Way
Which space observatory has detected and precisely located over 900 GRBs?
NASA's swift.
Within the disk of the galaxy, what sort of clusters of stars can typically be found?
Open clusters (only)
Our Sun is located just outside one of the smaller arms called
Orion Arm
What type of galaxy has a shape that's weird and distorted?
Peculiar galaxies
Spiral galaxies have spiral arms with a distinct bluish color, caused by what?
Recent and ongoing star formation
Sort the following three objects into size from smallest to largest
Solar System, Milky Way, Local Group
What type of galaxy is the Milky Way?
Spiral
At visible wavelengths, some regions of the Milky Way's disk appear dark because
Stars in that direction are obscured by interstellar dust
Clusters of galaxies themselves fall into even bigger groups called
Superclusters
Which telescope was used to search for evidence of black holes at the cores of galaxies?
The Hubble Space telescope
What is the biggest and most active star-forming gas cloud in any nearby galaxy?
The Large Cloud
Our Milky Way is part of a small knot of a few dozen galaxies that we call
The Local Group
The small cluster of galaxies to which the Andromeda galaxy belongs is
The Local Group
Our "hometown" is a vast, disk-shaped collection of stars called
The Milky Way Galaxy
Which two galaxies completely overpower the Local Group?
The Milky Way, and the Andromeda Galaxy.
Which two countries were the first to develop nuclear weapons?
The US and USSR
Why would we expect the bulge of a galaxy like ours to look redder than the disk?
The bulge consists mostly of old stars; the disk includes young stars
What object sits at the very center of our galaxy?
The bulge: spherical bar of redder stars
The predominant model of galaxy formation is
The hierarchical model, where small galaxies formed first and then merged into larger and larger galaxies
What makes the central part of our galaxy harder to study than in many other galaxies?
There is a lot of gas and dust between us and the center
Why are white dwarf supernovae such a useful distance method?
These are some of the brightest events in the universe, so you can see them at enormous distances
A property that is not generally true of spiral galaxies is
They are typically the largest type of galaxies (central dominant)
How many major spiral arms are in the Milky Way Galaxy?
Two
If viewed edge on, our galaxy would probably most resemble what shape?
UFO type shape
Our galaxy is especially difficult to observe than many other galaxies because
We are right in the plane of our galaxy, where the most gas and dust is
How can we possibly know what typical galaxies were like or what they were doing billions of years ago?
We can look at newly formed galaxies now, and assume that ancient galaxies looked the same when they were young
How can we typically measure how fast a galaxy is rotating?
We measure the Doppler shift of the 21 cm line from different parts of the galaxy
Which of the following is false about galaxy collisions?
When they collide, the stars in them often collide, destroying them
If the poles of an active galaxy are aimed right at us, we see energetic
X-ray and gamma-ray light.
The redshift of a galaxy is
a. How much redder the galaxy appears when observed at large distances b. The recessional velocity of a galaxy, expressed as a fraction of the speed of light
A massive star that explodes with more energy than a normal supernova is called an
accretion disk.
The flat disk of material that swirls around a black hole is called an
accretion disk.
Galaxies that emit x-rays and gamma rays were given the generic name
active galaxies
Often have radio jets extending from their cores, aligned with their minor axes
active galaxies
The spectrum of the Andromeda Galaxy is blue-shifted, which means it's
approaching us
Every time we see a gamma-ray burst, we're witnessing a
black hole being born.
Most large galaxies, including the Milky Way, likely grew to their current bulk by
consuming smaller galaxies
The mysterious bursts of gamma rays were determined to be coming from deep space.
deep space
Giant spheroidal galaxies typically having no apparent structure
ellipticals
In the 1960s, the peculiar object 3C273 was eventually determined to be an
entire galaxy
(T/F) Elliptical galaxies often have significant amounts of gas and dust
false
The patchy arms, that resemble tufts of cotton, in some spiral galaxies, are called
flocculent spirals
Current thinking is that elliptical galaxies are the products of
galactic collisions
One way to flip a quiescent black hole from a baby to a monster is through
galactic collisions
Massive objects revolving around each other lose orbital energy by radiating away
gravitational waves
The Vela satellites, launched by the US, were designed to detect
high-energy pulses of gamma rays.
There are two types of GRBs. The ones that last longer than two seconds come from
hypernovae
Early maps of the galaxy, which placed the Sun near the center, didn't account for
interstellar dust
Have very chaotic structure with no apparent symmetry
irregulars
The vast spherical cloud of old stars surrounding the Milky Way is called
its halo
For Cepheid variables, the time it takes them to pulse is directly related to their
luminosity
What is thought to be the source of energy in the nuclei of active galaxies?
massive black holes
Ancient Greeks called the glowing pathway in the sky "galaxius", which means
milky
Before 1920, "faint fuzzies" displaying a variety of shapes in the sky were simply called
nebulae
The cylindrical bar at the center of our galaxy is composed mostly of
old red stars
The most powerful energy source in the entire cosmos was dubbed, for short,
quasar
The words "irregular" and "peculiar" are used to classify galaxies based on
shape
GRBs were detected to be coming from galaxies as far away as
six billion light-years away.
Disks with central bulges surrounded by spherical halos of old stars
spirals
The spiral arms of our galaxy can best be thought of as
structures; huge collections of stars and nebulae moving together around the galaxy's center.
If GRBs were from neutron stars then we'd see them along
the plane of the milky way
(T/F) A spiral galaxy has both old and young stars
true
(T/F) When two galaxies merge, new stars are often formed in the process
true
The shorter GRBs that last only milliseconds come from
two neutron stars crashing into each other and exploding
10. Star-forming nebulae in spiral arms are colored pink by the characteristic glow of
warm hydrogen